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VERY WELL 3 L-THIA estimates match measured direct runoff separated from USGS daily stream flow using iSep VERY WELL. How Good is L-THIA ?

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3 Versions of L-THIA System Very Efficient in Assessing Impacts of Urbanization on Water Environment (compared to other complex models, while providing reasonable accuracy) 3 Very Easy to Use / Easy to Obtain Model Input, (compared to other complex models, while providing reasonable accuracy) 3 Available from - https://engineering.purdue.edu/~lthia/ SUMMARY

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Low-Impact Development (LID) An approach to land development to mimic the pre-development site hydrology to: 1)Reduce volume of runoff 2)Decentralize runoff, diffusing flows into smaller retention/detention areas 3)Improve water quality 4)Encourage groundwater infiltration

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Purdue University is an Equal Opportunity/Equal Access institution.

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Purdue University is an Equal Opportunity/Equal Access institution.

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Purdue University is an Equal Opportunity/Equal Access institution. Porous or permeable pavement, sidewalks, driveways are surfaces that infiltrate, constructed from a range of materials.

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Purdue University is an Equal Opportunity/Equal Access institution. Permeable Pavement and Permeable Patio Permeable pavements or asphalts are generally used to capture and filter runoff from impervious parking lots, driveways, streets, roads, and patios, thus controlling NPS pollution loading (Dietz, 2007). While traditional pavements turn almost all rainfall into runoff, permeable pavements encourage infiltration of rainfall by creating extra moisture in the soil profile. The original CN value of 98 for conventional asphalt was changed to 70, 80, 85, and 87 for driveways and sidewalks with porous materials as suggested by Sample et al. (2001).

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Purdue University is an Equal Opportunity/Equal Access institution. This land use is 1/8 acre lot, high density residential. The default assumption is 871 ft2 of pavement per driveway per lot. To cost the porous pavement option, user assumes 8 lots this size per acre. Cost table has range of $2 to $12 per ft 2 of pavement. Estimate could be $10.00 times 8 lots times 871 ft 2 = $ / acre

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Purdue University is an Equal Opportunity/Equal Access institution.

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Purdue University is an Equal Opportunity/Equal Access institution. Green Roof Green roofs have been used for many years, especially in Europe, to retain precipitation, provide insulation, and create habitats for wildlife (Miller, 1998; Rowe, 2011). Green roofs have also been credited for lowering urban air temperature and help reduce heat island effects (Miller, 1998; Rowe, 2011). Depending on the thickness of the layers used and the extent of required maintenance, green roofs can be portrayed as extensive or intensive (GRRP, 2010). Green roof was represented using the value of 86 for runoff CN for the 4 HSGs (Sample et al., 2001).

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Purdue University is an Equal Opportunity/Equal Access institution. Green Roofs vary widely in complexity and cost. Low estimate $ 8.50 per square foot High estimate $ per square foot. Next slide is an example with 28 commercial acres with 25% roof, or 7 acres of roof. That creates * 7 = ft 2 feet of roof. And this proposal is that 50% of the roof will have LID practice: Mid-range cost of $ ft 2 times 0.50 % of ft 2 is $ 4.4 million.

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Purdue University is an Equal Opportunity/Equal Access institution. Per Cent of roof treated with BMP Total area of this landuse Per Cent of area which is roof Green Roof

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Purdue University is an Equal Opportunity/Equal Access institution. Rain Barrel and Cistern Installation of rain barrels and cisterns in residential subdivisions allows harvest of rainfall water for potential reuse. In many countries with water scarcity problems, especially in developing countries, the use of vertical storage systems, tanks, and underground storage structures is a common practice and serves as good water supply reservoirs. The value of runoff CN used to represent rain barrels is 94 and cisterns is 85 for the 4 HSGs (Sample et al., 2001).

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Purdue University is an Equal Opportunity/Equal Access institution. For a median price barrel assume $200 each; The model assumes one per homeowner. High density residential 1/8 acre lot land use would require 8 barrels per acre if practice is 100%; 4 barrels /ac at 50%. $ 1600 per acre of 1/8 acre lot residential landuse at 100% LID. Rain Barrels may be installed by volunteers or professionals, so costs vary.

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Purdue University is an Equal Opportunity/Equal Access institution. Bioretention Systems Bioretention systems consist of shallow depressions designed for holding stormwater runoff from impervious surfaces such as parking lots, rooftops, sidewalks, and drive ways. They promote infiltration by allowing rain water to soak into the ground, thus reducing runoff that can potentially enter stormwater systems. Bioretention systems also support runoff filtration for water quality improvement with planted non-invasive vegetation. The values of runoff CN used to represent hydrologic benefits of bioretention systems are 35, 51, 63, and 70 for Hydrologic Soil Group (HSG) A, B, C, and D, respectively.

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Purdue University is an Equal Opportunity/Equal Access institution. Design of bioretention systems is very site-specific. The L-THIA LID practice is applied as a benefit (to the curve number) for the entire acre. The size is generalized and assumed to be adequate. A typical size (for cost estimates) for a residential lot could be 100 ft 2.

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Summary  L-THIA LID is a screening tool to evaluate the benefits of LID practices  L-THIA LID provides an easy to use interface  Will enable decision makers to formulate watershed management plans to meet goals  Along with other tools, allows stakeholders to understand impacts of water quantity and quality resulting from land use change  https://engineering.purdue.edu/~lthia/ https://engineering.purdue.edu/~lthia/

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Accountability Are the tools in use? Who is using the tools? How can they be improved? Are browser or script issues a problem? Is navigation clear? Purdue University is an Equal Opportunity/Equal Access institution.